Microphonic telephone



. (No Model.) I

- T. A. WATSON.

Mierephonio Telephone.

No. 242, 23. Patented June 7,1881;

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N. PETERS. PhanLillwgmplwr. Wnhinglnm D. (Iv

UNITED STATES PATENT OFFICE.

THoMAs A. WATSON, on EVERETT, MAssAcHUsETTs.

MICROPHONIC TELEPHONE.

SPECIFICATION forming part of Letters Patent No. 242,723, dated June 7, 1881.

Application filed April 8, 1881.

To all whom it may concern:

Be it known that I, THOMAS A. \VATSON, of

, Everett, in the county of Middlesex and State of Massachusetts, have invented. certain Improvements in Microphonic Telephones, of which the following is a specification.

My invention relates to that class of instruments known as microphonic or contact telephones, in which the mechanical vibrations resulting from the impact of the sound-waves on the transmittirig-diaphragm act upon a va riable resistance included in the circuit in such a manner as to cause it alternately to increase and diminish, thus throwing the continuous current of a voltaic battery flowing in the circuit into electrical undulations of greatlyvarying degrees of. strength or intensity. The atmospheric vibrations being thus, so to speak, transmitted into nndulatory currents of electricity, these, in turn, are made to develop corresponding mechanicai movements at the receiving-station, whereby at that point the air is caused to vibrate and the original sounds reproduced in suitable receivers.

Heretofore such telephones, whether employed for the transmission or reception of vocal sounds, have been constructed with a diaphragm rigidly clamped to the frame, a conducting-electrode more or less rigidly attached to the diaphragm, and a second electrode normally maintained in contact with the first by a certain initial pressure and suspended on a spring or pendulum. Other forms of battery telephones have been made in which both electrodes and diaphragm are rigidly supported.

Experiencehas demonstrated that in instruments of the first class the spring or pendent electrode, not being entirely under control of the sound-waves, will introduce extraneous vibrations, which, not belongingto the sounds intended for transmission, consequently tend to confuse and render them indistinct.

Experience has also manifested the fact that battery-telephones of the second class, by reason of the inflexibility of the diaphragm and electrodes, have such a limited range of adj ustment that in practice they cannot be used with a great degree of success for any protracted period of time. When such transmitters are,

however, brought to their proper adjustment 7,

an adjusting-spindle, d, which, by its milled they give much better results than those pro- (No model.)

vided with a rigid diaphragm and spring or pendulous electrodes.

The objects of myinvention, generally speakin g, are to improve the strength and steadiness of the transmitted tones, to form an improved and delicate receiving contact-telephone, and

generally to increase the efficiency of the instrument. These endsI attain by suspending,

by a hinge, spring, or pivot from a support attached to the frame or casi n g of the telephone, a diapl'iragm carrying a conducting contactpoint or electrode, of carbon or other suitable material, and also in the combination of the same with a rigidly-mounted complementary electric contact-point, which may be adjustable, and with which it is normally maintained in contact by the gravity of the suspended diaphragm.

In the accompanying drawings, Figure 1 is a sectional view of my improved contact-telephone. Fig. 2 is a sectional view on the line to a; of Fig. 1, looking at the diaphragm; and Fig. 3 is a diagrammatic view of a telephonecircuit, showing my apparatus used at one station as a transmitter and at the other as a receiver.

In the figures, A is the casing or box inclosing the working parts, and to which the front piece, B, is attached. This front board, B, is made of wood or any other suitable material, and in its center is fixed the mouth-piece G, which passes completely through the board B,

and is secured with its inner end in close proximity to the diaphragm D near its center. The diaphragm D has a rubber ring fastened round its edge, and at its upper edge has a hinge, g, fastened to it by the rivet h. It is suspended by the hinge from the horizontal brass plate f, which is firmly fixed to the wooden part of the frame B by screws. To one of the screws holding the brass plate is connected the wire 10, constituting the path by which the batter current is led through the microphone. It is metallically connected, through the plate f, hinge g, rivet h, and diaphragm D, to a carbon contact-point or electrode, b,which is, by means of a screw, attached to the center of the diaphragm at its inner side. i

A second carbon button or stud, 0, arranged in a setting of brass, is carried on the end of head e, is screwed up until the second carbon button, which forms the opposing or complementary contact-point or electrode, touches the first and presses lightly against it, keeping it thereby from reaching its point of rest. The proper degree of pressure may readily be attained by varying the adjustment of the screw d. To the metallic socket in which the adjusting-screw works, or to any part of the casin g in metallic connection with the screw d, the wire to is connected, thus completing the circuit through the contact-points b c.

In Fig. 3,1 represents a telephone-station at one end of the line to, while 2 is a corresponding station at the other end. P is a battery, included in the circuit, and the circuit is shown as terminating at both ends in the earth. At such end of this line I have shown an instrument such as I have described with a pendulous diaphragm and a rigidly-mounted or inflexible opposing electrode. In this arrangement I have availed myself of a principle of electrical science which may be stated as follows: that if two electrodes be placed in contact to complete a circuit and a current of electricity be passed through them, a repulsion is exerted between the points, and that the force of repulsion may be weakened and strengthened by varying the strength of the current.

On this principle my invention is well adapted for use as a receiving-telephone, and the telephones shown at each end of the line in Fig. 3 are supposed to be used alternately as transmitters and receivers for it is apparent that as the pencil-electrode attached to the adjusting-screw is rigid and immovable, and the diaphragm D, carrying the button-electrode b, is freely suspended and readily vibrated, the effect of any repulsion between the contacts I) and 0 will be inevitably expended on the diaphragm, whereas in the ordinary forms of spring or pendulous electrode instruments the force is expended in moving the electrode without materially affecting the diaphragm.

In an application previously filed by me I have shown a diaphragm mounted on three springs and capable of axial vibrations on a rigid or immovable contact-point, which form of construction is consequently not herein claimed.

As a rule in operating it will be found preferable to place the instrument in the primary circuit of a suitable induction-coil and connect the secondary circuit of the coil with the linewire or conductor extending to the distant station in a manner well understood.

What I claim as my invention, and desire to secure by Letters Patent, is-

1. In a contact-telephone, the combination of a freely suspended diaphragm or vibrating surface, carrying a conducting contact-point or electrode, with a rigidly-mounted opposing electrode, and with which it is normally main- 'tained in contact by the gravity of the suspended diaphragm, substantially as described. 2. Theimproved contactreceiving-telephon e, consisting of a diaphragm or "ibrating plate freely suspended in an unconfined air-space and carrying a condnoting-electrode, the rigidly-mounted or inflexible opposing electrode in contact with the first, and the mouth-piece 0, all arranged substantially as and for the purpose specified.

3. In a contact-telephone, a diaphragm or vibratory surface freely suspended by a hinge, spring, or pivot, in combination with a rigidlymounted contactpoint, substantially as described.

In testimony whereofI have signed my name to this specification, in the presence oftwo subscribing witnesses, this 6th day of April, A. D. 1881.

THOMAS A. WATSON.

Witnesses:

EMILE BERLINER, Tnos. D. LooKwooD. 

